Apparatus and method of forming ophthalmic lenses



April 19, 1960 E. T. DALTON 2,932,925

APPARATUS AND METHOD OF FORMING OPHTHALMIC LENSES Original Filed Feb.20, 1956 9 Sheets-Sheet 1 N VEN TOE ERNEST 7. DHLTON A TTOENEY April 19,1960 E. T. DALTON APPARATUS AND METHOD OF FORMING OPHTHALMIC LENSES 9Sheets-Sheet 2 Original Filed Feb. 20, 1956 m T N E V m EENEST 7T.D/MTON ENE)" ATTO April 19, 1960 E. 'r. DALTON 2,932,925

APPARATUS AND METHOD OF FORMING OPHTHALMIC LENSES Original Filed Feb.20, 1956 9 Sheets-Sheet 3 IN VENTOR ERNEST 7T DALTON April 19, 1960APPARATUS AND METHOD OF FORMING OPHTHALMIC LENSES E. T. DALTON 9Sheets-Sheet 4 IN VEN T02 ERNEST T DALTON ATTOENEY April 19, 1960 E. T.DALTON 2,932,925

APPARATUS AND METHOD OF FORMING OPHTHALMIC LENSES Original Filed Feb.20, 1956 9 Sheets-Sheet 5 //v VEN r0? ERNEST 7. .DHL TON A T me/vg YApril 19, 1960 DALTON 2,932,925

APPARATUS AND METHOD OF FORMING OPHTHALMIC LENSES Original Filed Feb.20, 1956 9 Sheets-Sheet '7 IN VE N TOE EBA/E157 7. DHLTON HTTOE EY April19, 1960 E. T. DALTON 2,932,925

APPARATUS AND METHOD OF FORMING OPHTHALMIC LENSES Original Filed Feb.20, 1956 9 Sheets-Sheet 8 54 55 "jig/6 IN VEN TOR ERNEST 7- DALTON H TTORNE Y April 19, 1960 E. T. DALTON 2,932,925

OPHTHALMIC LENSES APPARATUS AND METHOD OF FORMING Original Filed Feb.20, 1956 9 Sheets-Sheet 9 /N VEN TOE EQNEST 7." 00L TON 2 73.79 fiwATTORNEY APPARATUS AND METHOD OF FORMING (BPHTHALMIC LENSES Ernest T.Dalton, Sturbridge, Mass., assignor to American Optical Company,Southbridge, Mesa, a voluntary association of Massachusetts 9 Claims.((151-131) This invention relates to improvements in apparatus StatesPatent 2,932,925 Patented Apr. 19, 1960 embodying the invention withportions of the protective coverings removed therefrom;

Fig. 5 is a sectional view of one of the cup-shaped abrading tools ofsaid lens generating device;

Fig. 6 is a diagrammatic illustration of the rough gen erating of thelens blanks embodying my invention;

Fig. 7 is a view generally similar to Fig. 6 illustrating the finegenerating of said lens blanks;

Fig. 8 is a fragmentary sectional view taken substantially on line 88 ofFig. 4 and looking in the direction of the arrows;

for forming multifocal lenses and has particular reference to theprovision of novel means for simultaneously forming a plurality ofone-piece multifocal lenses of the type having wide focal fields and arelatively straight line of division between said fields.

The instant application is a division of the inventors co-pendingapplication for patent Ser. No. 566,688 filed February 20, 1956 whichissued as Patent No. 2,890,551, dated June 16, 1959.

In the manufacture of multifocal lenses, it has been found that byforming the desired focal fields upon a single piece of lens mediumsuperior quality may be ob tained since past difficulties of expansion,interfacial defects, chromatic aberrations, etc., commonly encounteredin forming multifocal lenses of the fused type embody ing two or morepieces of different glasses, are eliminated. However, prior processes offorming such onepiece multifocal lenses have required the use ofrelatively involved, complicated and expensive manufacturing techniqueswherein each lens had to be formed individually. This not onlyrestricted production, but increased cost and greatly restricted themarketing of such lenses.

it, therefore, is a principal object of the present invention to providenew and improved apparatus for producing a plurality of such one-piecemultifocal lenses simultaneously with controlled optical characteristicsand with the straight transversely extending line of division betweenthe focal fields maintained at a practical minimum height.

Another object is to provide improved apparatus for forming lenses ofthe above character wherein the power introduced in the respectivefields and the related optical centers thereof may be simply andaccurately controlled.

Another object is to provide novel means for simultaneously generating areading field of controlled power upon a portion of each of theoptically finished distance fieids of a plurality of lenses wherein saiddistance and reading fields will be divided by straight transverselyextending lines of division passing substantially through the respectiveoptical centers of said distance and reading fields.

Other objects and advantages of the invention will become apparent fromthe following description taken in conjunction with the accompanyingdrawings in which:

Fig. l is a perspective view of a lens blank formed in accordance withthe invention;

Fig. 2 is a sectional view of the lens blank taken on line 2-2 of Fig. 1looking in the direction of the arrows and including a diagrammaticillustration of the centering of its different focal fields;

Fig. 3 is a side sectional view of a preferred type of lens blockingapparatus to be used with the embodiment of my invention;

Fig. 4 is a top plan View of a lens generating device Fig. 9 is anenlarged sectional view taken on line ,9-9 of Fig. 4 and looking in thedirection of the arrows;

Fig. 10 is a fragmentary sectional view taken on, line 10-10 of Fig. 9looking in the direction. of the arrows;

Fig. 11 is a fragmentary sectional view taken substantially on line 1111of Fig. 8 and looking in the direction of the arrows;

Fig. 12 is a diagrammatic illustration of a type of polishing apparatusto be used in connection with the embodiment of the invention;

Fig. 13 is a schematic illustration of the electrical circuit forautomatically controlling the operation of the above lens blankgenerating device;

Fig. 14 is a fragmentary top plan view, partially in cross-section, of amodification of a part of the lens generating device which isillustrated in Figs. 4, 8, 9 and Fig. 15 is a fragmentary sideelevational view, partial ly in section, of the modified part of thelens generating machine which is shown in Fig. 14;

Fig. 16 is a fragmentary front elevational view shown partially incross-section of the part of the device shown in Fig. 14;

Figs. 17 and 18 are diagrammatic illustrations of different stages inthe lens generating operation which is performed with the lensgenerating device of the invention when said device is modified as shownin Figs. l4 16; and

Fig. 19 is an electrical diagram which schematically illustrates thecircuitry involving the electrical operation of the modification of theinvention shown in Figs. 14-.- 16.

Referring more particularly to the drawings wherein similar referencecharacters represent similar parts throughout the various views thereof,one .form of a finished lens blank L embodying the invention is shown inFig. 1 and comprises a single piece of lens medium, preferably opticalcrown glass or the like, having an upper or distance field 10 and alower or reading field 11. The fields 10 and 11 are separated by astraight dividing line 1'2 which passes through the optical axis of thelens blank so as to provide said lens blank with a wide read ing field11 extending transversely throughout the width thereof.

Referring more particularly to Fig. 2, wherein dotdash line 13represents the optical axis of the finished lens, it can be seen thatthe center of curvature 14 of the distance field 10 and the center ofcurvature 15 of the reading field 11 both lie on said axis line 13 andthe optical centers 16 will, therefore, be in monaxial relation witheach other and will lie on the dividing line 12 as illustrated in Figs.1 and 2. Moreover, it is to be noted that the centers 14 and 15 of thecurvatures of fields 10 and 11, respectively, are so positioned alongthe optical axis 13 as to provide a near mergence of said curvatures atsaid optical centers 16 and thus cause the dividing line 12 to bereduced to a practical minimtun height adjacent said centers. Thisrelation of the centers 16 substantially eliminates the error of jumpwhen the other. Dividing line 12, however, produces a ledge 17 whichprogressively increases edges of the lens blank, which height on theopposed sides of the centers 16 is determined by the differenceincurvatures of the fields 1d and ll.

The finished lens is formed'by providing the opposed side of the lensblank with a finished optical surface 18 of a curvature which is suchthat when combined with the curvatures of the fields 1i) and ll, it willgive the required powers in said fields. The final thickness desired ofthe finished lens is controlled by the depth to which the surface 18 isformed.

In carrying out the simultaneous forming of a plurality of lens blanksof the above character in accordance with this invention, a plurality oflens blanks L (see Fig. 3), preferably of optical crown glass or thelike, having on the convex sides thereof a continuous referencesurface10a substantially of the curvature desired for the distance portion ofthe finished lenses and all having substantially the same thickness andcontour shape are provided. The reference surfaces 10a of the blanks maybe optically finished or semifinished and in the latter case, they wouldbe finally optically finished subsequent to the forming of the readingfields 11. The reference surfaces lda are initially provided on the lensblanks by any one of the known standard methods of grinding and/orpolishing which preferably incorporate the use of a multiple blockingarrangement for reasons of economy and the curvatures of the referencesurfaces will be referred to hereinafter as the base curves of the lensblanks L.

1 It is to be understood that the term multifocal as used in thisspecification and accompanying claims is intended to mean lenses havingtwo or more focal fields. However, in the description immediatelyfollowing, the process of manufacturing lenses having only two focalfields, namely, a distance portion and a reading portion will bediscussed. However, it will become apparent that lens blanks having morethan two focal fields may also be manufactured with the use of theapparatus shown and described herein.

The lens blanks L are first mounted upon the outer annular surface of awheel-type block B by means of a precision blocking mechanism such asshown in Fig. 3 of the drawings.

The size of block B, however, must be selected in accordance withtheparticular surface curvature to be ultimately provided upon the readingfield of the lens blanks which are mounted thereon. That is, the radialdistance from the axis of rotation of the block to the lens blankmounting surfaces must be controlled in accordance with the desiredradius of the curvature to be applied to the reading field so as topermit a relatively thin layer of pitch or suitable adhesive to beapplied between the lens blanks L and said mounting surface of theblock. However, in order to maintain a precise radial distance from theaxis of rotation of the block to the ultimate reading portion surface 11to be formed on the blanks L, which radial distance is equal to theradius of curvature of the reading portion curve, hereinafter referredto as the RP curve, precision spacer stops 46 specifically designed foreach change in added power of the RP curves are used in conjunction withthe blocking mechanism of Fig. 3. By so controlling the size of block B,the thickness of the above-mentioned pitch or adhesive between blanks Land the mounting surface of said block is maintained relatively thin andsubstantially constant throughout the range of the various sizes ofblocks required for mounting blanks L. Any shrinkage of the pitch duringits in height toward the outer hardening would then be negligible andwould not ad versely affect the subsequent generating procedure.

The blocking mechanism of Fig. 3 comprises a base 32 having a verticallyextending block carrying shaft 33 mounted for reciprocal movementtherein. The upper end of shaft 33 is provided with a right-angledforwardly extending block supporting arm 34 rigidly secured theretoandhaving a reduced axle portion 35 of a diameter precisely controlledto intimately receive the hub portion 36 of the wheel-like block B. Inaddition, the axle portion 35 is rigidly mounted on arm 34 by studs 35awith its longitudinal axis normal to the longitudinal axis of shaft .33and is provided with a locating pin 37 which is adapted to engage one ofa plurality of matching orifices 37a in block B, when assembledtherewith, to prevent rotation of said block relative to said axleportion 35 for purposes of indexing block B relative to the base 32 whenapplying lens blanks thereto as will be described immediatelyhereinafter.

In order to restrict shaft 33 from rotation and thus maintain axleportion 35in a fixed transverse location relative to the base 32, arestraining arm 38 is secured at one end to shaft 33 and has its opposedend slidably mounted, in a vertical direction only, on a guide spindle39 which, in turn, is rigidly secured in the base 32.

A removable blocking mould td generally square in shape is positioned.in a recessed portion 41 of the base 32 and has its axis aligned with aline passing through the center of the width of the block B andintersecting the axis of the axle portion 35 at substantially rightangles thereto and consequently similarly intersecting the axis ofrotation of the block B when said block is placed on the axle 35. Mould40 is provided with lens locating pins 42 of uniform length in eachcorner thereof for supporting a lens blank L when positioned thereinwith the general plane of its reference surface 10a in normal relationto the axis of the mould 4d. The mould 40 is further provided withupwardly extending side portions 43 for engaging the edges of a lensblank L when placed therein and locating the geometricalcenter of saidlens blank on said axis of the mould 46 whereby the axis of thecurvature of the reference surface of said lens blank will intersect theaxis of rotation of block B and be aligned substantially normal thereto.

It is pointed out that mould 40 may be of any desired shape such as tomatch that of the particular lens leaks to be fitted therein so as tointimately receive the side edges of said lens blank between the sideportions 43 of the mould 40 and locate the geometrical center of thelens blanks substantially on the axis of the mould 40 at all times.

The blocking mechanism is further provided with a vacuum line 44 whichis connected to the blocking mould recessed portion 41 for the purposeof setting up a vacuum of an amount to retain a lens blank properlyseated on the pins 42. An air cylinder 45 or any other suitablemotivating means is connected to the shaft 33 for the purpose ofpneumatically moving the said shaft and the block B toward or away fromthe blocking mould 40.

Operation of the blocking mechanism is as follows:

Each of the lens blanks to be mounted on block B is provided with asuitable bonding agent upon the surfaces thereof opposed to thepreviously mentioned reference surfaces. In the case of the partciularprocess illustrated and described herein, the bonding agent wouldbeapplied to the concave surfaces of the blanks. Although various types ofbonding agents and methods of applying same to the blanks may be used,it has been found preferable to place a pellet or wafer of pitch or thelike on the concave surface of each of the lens blanks and, in turn,place said lens blanks in a suitable oven or heating chamber tocontrollably heat and soften the pitch. The blanks are then removed, oneat a time, from the heating chamber and placed in the blocking mould 40with the convex reference surface resting on pins 42 as shown in Fig. 3.

Attachment of a particular lens blank to the annular mounting surface ofthe block B is then accomplished by causing shaft 33 to be drawndownwardly upon proper actuation of air cylinder 45 whereupon the blockwill engage the softened pitch. However, since it is necessary toprecisely control the radial distance from the axis of the block to thereference surface of the blank in accordance with the desired radius ofcurvature to'be applied to the reading portion thereof, which radiuswill be equal to the desired radius of the RP curve, a re-' movablespacer stop 46 of a precisely controlled thickness is placed upon ashouldered portion 47 of the base 32 adjacent the shaft 33 so as to beengaged by the under surface 48 of the arm 34 and thus limit the extentof downward movement of shaft 323 and so locate the axis of block B at apredetermined distance above the blocking mould 40.

Since each desired change in power of the RP curve requires a change inthe radial distance from the axis of block B to the reference surface ofthe blanks mounted thereon, a particular spacer stop .6 of a controlledthickness is provided for each RP change within the range of powerswhich may be used with a particular block B.

It can then be seen that by controlling the distance from the tops ofpins 42 in mould 40, upon which the reference surfaces of the lensblanks are seated, to the plane of shoulder 47 and by the properselection of the thicknesses of spacer stop 46, the desired RP radius isobtained and the remaining space between the concave surface of theblanks and the mounting surface of block B will be filled by the pitch.

The vacuum line 44 is used to create a partial vacuum internally ofmould 4i) and thus retain a lens blank properly seated upon pins 4-2during the blocking operation.

The above blocking operation is repeated by properly actuating aircylinder 45 and causing shaft 33 and block B to be raised, thus liftingthe lens blank now attached thereto out of mould 40 since the adherenceof the pitch is sufficient to overcome the holding force of the vacuumcreated internally of mould 40. Additional blanks are positioned one ata time in mould 40 in the above described manner and the block B isindexed to a clear position on the mounting surface thereof prior toeach application by partially withdrawing block B from axle 35 an amountsufiicient to clear the locating pin 37 and rotating said block B to aclear position on the mounting surface thereof which will be alignedwith a second orifice 37a. The block B is then pushed inwardly upon axle3S, whereupon locating pin 37 will engage in said second orifice 37a toproperly locate block B relative to mould 40 and the operation describedabove is repeated for each lens blank until the desired number of lensblanks are mounted upon the mounting surface of block B.

It is pointed out that the number of lens blanks which may be applied toa particular block is dependent upon the RP radius and also the outercontour size of the lens blanks to be applied thereto. Moreover, thelens blanks are preferably positioned in close edge-to-edge relationwith each other about the lens block mounting surface and if the relatedsizes of the block and lens blanks are such as to leave a relativelywide spacing between the first and last lens blanks mounted thereon, itis also preferable to fill said space by similarly mounting a glassfiller of substantially the same thickness as the lens blanks betweensaid first and last mounted lens blanks. This provides a substantiallycontinuous glass surface to be abraded and polished in the operations tofollow and allows the abrading and polishing tools to pass over saidspace without sharply striking the edges of the adjacent lens blanks.

it is also pointed out that in order to maintain the above-mentioneddistance from the top of pins 42 in mould 40 to the plane of shoulder 47substantially constant, in connection with each change in block size, itis necessary to provide an individual. mould 47 of the proper height andhaving proper length of pins to bring about this result. The block sizeis determined by the RP curve of the lens blanks to be processedthereon, as described hereinabove.

After having blocked the lens blanks in the above manner, the block B isthen removed from the blocking device and the desired RP curve isgenerated upon the reference surfaces of the lens blanks in thefollowing manner.

The block B and attached lens blanks L are secured on one end of and inaxial alignment with a rotatable spindle 50 of the lens surfacegenerating device, illustrated in Figs. 4, 8, 9, l0 and 11 of thedrawings. Spindle S0 is initially positioned substantially midwaybetween a pair of rotatable angled cup-shaped rough and fine, preferablydiamond charged, abrading tools 51 and 52 respectively. Said tools areeach adapted to be pivoted at points 51a and 52a respectively and angledwith respect to spindle 50 so as to have their axes of rotation in acommon plane with, and each intersecting the axis of the spindle 50.Furthermore, the pivot points 51a and 52a are each located at the lowestpoint on the cutting edge of the respective tools, and since it isdesired that the dividing line 12 of the finished lens blanks L beformed to extend transversely through the ultimate location of theoptical centers 16 therefore, the pivot point 52a of the fine or finishabrading tool 52 is positioned so as to lie in a horizontal planepassing through said ultimate location when block B is positioned uponspindle 50, as illustrated best in Fig. 8. Pivot point 51a, however, ispositioned slightly above said horizontal plane preferably about of aninch to cause the cutting edge of the coarse or rough abrading tool toinitially rough form said dividing line 12 on lens blanks L slightlyabove the ultimate location of the optical centers 16 thereof.

This slightly raised condition of tool 51 is provided to protect theimmediate area in which the dividing line 12 is to be finally formed bytool 52 from damage due to possible glass flaking which might be causedby the coarseness of the abrading particles of tool 51. It is pointedout that the tool 51 is only used to form the general shape of the finalRP curve as will become apparent from the description to follow.

Tools 51 and 52 are preferably provided with a controlled diameter D anda formed radius of curvature R, Fig. 5, upon the cutting edges thereof,radius R being equal to the radius of curvature of the RP curve to begenerated on blanks L. A particular pair of tools 51 and 52 is providedfor each desired change in RP curvature and the radius R of said toolsis designed to cause a true continuous RP curvature to be generated fromthe ledge 17 of blanks L to the outer edges thereof when the tools areproperly angled with respect to the axis of spindle 50.

It should be understood that cup-shaped tools similar to the tools 51and 52 but having sharp or knife-like abrading edges may be used inplace of the preformed tools 51 and 52 if desired. However, wear uponthe sharp abrading edges of such tools tends to produce inferior abradedsurfaces or cliff-like dividing lines 12 on the lens blanks and it hasbeen found that the above described preformed tools 51 and 52 producethe best results.

The extent to which tools 51 and 52 are angled with respect to the axisof spindle 50 is geometrically determined by the ultimate RP curvedesired to be generated upon the blanks L. That is, for example, if itis desired to provide the blanks L with an RP curve of a 76.335 mm.radius, the tools 51 and 52 selected would have a cutting edge diameterof 3.125 inches, a radius R of 76.335 mm. and the rough abrading tool 51would be set at an angle of 3213 from the axis of spindle 50, whereasthe fine abrading tool 52 would be set at an angle of 3119 from the axisof spindle 50. However, if it is desired to provide blanks L with an RPcurve of a 66.769 mm. radius, the tools 51 and 52 would be selected tohave a diameter D of 3.125 inches, a radius R 66.769 mm. and tool 51would be angled to 3729 whereas tool 52 would be angled to 3628, etc.

It is pointed out that the tool dimensions and anguiar settings areprecisely calculated for each RP curvature required by the opticalprofession and that three major factors are necessary to generate thedesired RP curve on the lens blanks L. These factors are: first,blocking the blanks to provide a predetermined radial distance from theaxis escapes of rotation of the block to the surfaces of the blanks;second, selecting tools having the proper cutting edge diameters D andradii R and, third, properly angling each of the abrading tools withrespect to the axis of rotation of the block so as to generate in thetransverse meridian of the blanks a radius of curvature which issubstantially equal to the radius of curvature generated in a meridiannormal thereto and resulting from the rotation of said blanks about theaxis of the block. This is to cause said RP surfaces to be spherical inpower.

By referring to the diameter of the cutting edge of the abrading tools,it is intended to mean the diameter D, Fig. 5, measured at the apex ofthe leading abrading edge portion thereof.

The RP curve is then generated on the lens blanks L, by causing therotating spindle and blocked lens blanks L attached thereto to be movedtransversely in the abovedescribed common plane with the axes ofrotation of the abrading tools, so as to first engage the rough abradingtool 51 whereupon the abrading action of the tool 51, due to itsrotation and the rotation of lens blanks L about the axis of block B,will cause the straight line of division 12 and the ledge 17 to beformed simultaneously with the forming of, the RP curve which curve iscontrolled by the shape and angle of the tool and the radial distancefrom the axis of block B to the surfaces of blanks L. Said transversemovement is continued until the desired depth of cut is obtained. Sincethe tool 51 is of a coarse or rough abrading type which is used to formonly the general shape of the ultimate RP curve for purposes ofexpediting the generating operation, the rotating spindle SQ is nextcaused to retract from tool 51 and is moved in the opposite directionalong said plane an amount suflicient to cause the blanks L to engagethe tool 52 which is, in turn, the fine or finish abrading tool. SpindleSt) is caused to continue its transverse movement in the direction oftool 52 until a predetermined desired depth of finish cut isaccomplished. lo the case Where the reference surfaces ltla of the lensblanks are initially optically finished to the precise curvaturesdesired of the distance fields 1d of the lens blanks, the depth of cutis controlled to cause the newly generated RP curvatures to nearly:merge with the finished reference surfaces lila at the ultimate locationof the optical centers 16 of each of the finished lenses. However, ifthe reference surfaces 18a are initially semifinished, the depth of cutis controlled to be deeper and cause a slight shoulder to be left on thedividing line 12 at the location of the optical cen- I er 16 of thefinished lenses and in subsequently optically finishing the distancefields 10, the slight shoulder is recluced to a practical minimum. Whenthe lens blanks have been abraded by tool 52 to a desired depth of cut,the spindle 50 is caused to retract from tool 52 and assume its initialposition between tools 51 and 52. lt will be noted that due to therelative vertical positions of the tools 51 and 52 and the blockedblanks L, that approximately one-half of the side area of each of theblanks L is provided with the RP curve and the remaining half has theuntouched reference surface 19a thereon. This reference surfaceultimately becomes the distance viewing portion of the finished lens.

Referring more particularly to Figs. 6 and 7 which diagrammaticallyillustrate the forming of the ledge 17 on lens blanks L during thegeneration of the reading portion 11, it will be noted in Fig. 7 thatthe ledge 17 is finally finished to have its surface lie in the plane ofthe optical axis 13 of the lens blanks L which plane is also coincidentwith the pivot point 52a of the abrading tool 52.

Since it is preferred to have the plane of the surface of ledge 17substantially coincident with said plane of the optical axis 13 of thelens blanks L so as to prevent the undesired effects of prismdisplacement when the line of vision of the wearers eye passes overledge 17 while shifting from one focal field to another, the abradingedge portions of tools 51 and 52 are formed to controlled angular shapesfor each change in RP curve to be generated. That is, a different set oftools 51 and 52 each having a proper angularly shaped cutting edgeportion is selected in accordance with the degree of tilt required toproduce the desired RP curve and the said angle in each instance is suchas to cause the resultant cliif edge 17 of the dividing line 12 to beformed in a plane substantially parallel with the axis 13 and lying onsaid axis.

It will be noted in the previously described examples of the angularsettings of tools 51 and 52. that the angular setting of the roughabrading tool 51 for each particular RP curve is approximately onedegree greater than that of the fine or'finish abrading tool. Thisincreased ti ting of tool 51 about point 51a, in effect geometricallycauses the rough RP curve to be formed at substantially the same radiusof curvature as the fine RP curve which is generated by tool 52regardless of the above-mentioned slightly raised condition of tool 51which prevents possible slight flaking of the glass from reaching anddamaging the ultimate dividing line 12 of the lens blanks L.

As described hereinbefore, the tool 51 is used to form only the generalshape of the RP curve and ledge to cause the plane of the ledge 17 to beproperly formed substantially coincident with the plane of axis 13 sincethe fine grain of the abrading particles therein produce substantiallyno flaking of the glass and provides a clean out line of division 12between the adjacent fields 10 and 11.

It is particularly pointed out that due to the fact that the lowermostends or apices of the cutting edges of the tools are located on the axisof the pivots 51a and 52a, as shown particularly in Figs. 7, 8, and 9,no shifting of the position of said lowermost ends or apices withrespect to said axes takes place during the angling of the tool.

The block B is next removed from spindle and the final finishing of thegenerated RP curvatures is accomplished by a polishing operation to bedescribed herein-' after.

The above-described generating procedure, however, is automaticallyperformed by the generating device of Figs. 4, 8, 9, 10 and 11 whereinsaid device comprises in addition to tools 51 and 52 and spindle 50, abase 53 having a transversely slidable table 54 mounted on the uppersurface thereof. Spindle 50 is journaled in a vertically extendinghousing 55 which, in turn, is rigidly secured in the longitudinal bore56 of an enlarged depending supporting portion 57 of table 54. Rotationof spindle 50 is accomplished by means of a drive motor 58 which iscoupled to the lower end of said spindle 50 by a drive shaft 59 having apulley 60 mounted thereon and a connecting belt 61 engaging a secondpulley 62 which, in turn, is splined to shaft 5%). Said spindle drivemechanism is rigidly secured to and movable with table 554 by means of acombined motor bracket 63 and pulley housing 64 which housing is boltedor otherwise socured to the underside of the spindle supporting portion57 of table 54.

In order to move the table 54 transversely. along the top of base 53which path of movement is in the common plane of the axes of the spindle50 and of the tools 51 and 52 and is guided by suitable tracks orguideways 65, one at each side thereof, Figs. 8 and 11, a lead screw 66is rotatably secured at one end thereof by a bearing support 67 to thespindle supporting portion 57 of table 54 and the opposed end of saidlead screw 66 is threadedly engaged in a sleeve 68. Sleeve 68 is, intum, mounted for rotation in a stationary housing 69 rigidly secured tothe base 53.

As described hereinabove, the spindle 50, carrying block B, is to bemoved first into engagement with tool The finish abrading tool '52, Fig.8, is so angled as 51 and secondly into engagement with too! 52 andreturned to its initial position substantially midway therebetween toeffect the desired generating procedure. However, it is a well-knownfact in the trade that during a lens cutting or generating operation,the lenses must be fed relatively slowly into an abrading tool in orderto prevent undue flaking of the glass or damage thereto. For thisreason, the sleeve 68 is powered for rotation in either direction by acontrollable slow speed drive unit 70. However, in order to expedite themovement of lenses L on block B throughout their course of travelbetween their points of engagement with tools 51 and 52, lead screw 66is powered for rotation in either direction by a high speed drivemechanism embodying a high-speed reversible motor 71 having a sprocket72 on its shaft. A chain belt 73 is positioned upon sprocket 72 andextends upwardly and over a second similarly shaped sprocket 74 which iskeyed to lead screw 66. With the sleeve 68 held stationary in housing69, rotation of motor 71 in one direction will, through sprockets 72 and74 and chain belt 73, cause the lead screw 66 to rotate and advance intosleeve 68 thus drawing table 54 towards tool 51 whereas rotation ofmotor 71 in the opposed direction will cause lead screw 66 to retractfrom sleeve 68 and move table 54 in the opposed direction. Theslow-speed drive, however, is powered by a reversible motor 75 which isgeared to a horizontal shaft 76 having a worm gear 77 at its opposed endengaging a worm follower 78 on a second shaft 79 extending vertically toa second worm gear 80, Figs. 8 and 11. Worm gear 80 then engages asecond Worm follower 81 which is keyed to sleeve 68 whereby rotation ofmotor 75 will, through the above gears and shafts, cause sleeve 68 to berotated in housing 69.

In operation, motor 75 is initially de-energized which, due to theinherent braking effect of the worm gears and worm followers, preventssleeve 68 from rotating in housing 69 thus allowing motor 71 to beenergized so as to rotate in the proper direction to operate lead screw66, as described above, and rapidly move table 54 to bring the blanks Lto a point spaced a short distance from the tool 51 whereupon motor 71will be de-energized and stopped. Motor 71 is preferably of a typeembodying a conventional spring set magnetic braking means whichfunctions to brake and stop the rotation thereof when said motor isde-energized. By said braking effect, lead screw 66 will be heldstationary. Motor 75 is then energized to rotate at a given maximumspeed which is considerably slower than speed of motor 71 and, in turn,rotate sleeve 68 and cause lead screw 66 to be drawn inwardly thereofwhich will cause table 54 to continue its movement at a slower ratetowards tool 51. Upon reaching a point immediately prior to theengagement of lens blanks L with tool 51, the motor 75 is electricallycontrolled to cause table 54 to continue its movement toward tool 51 ata predetermined slower generating speed.

The purpose of including the first-mentioned slow speed of motor 75 isto provide a progressive slowing down of the table 54 from the rapidspeed of motor 71 to an ultimate still slower generating speed. Thisstill slower speed is brought about by an electrical variac in thecircuit of motor 75 and thus prevents any possible overtravel of motor71, during its braking period, from causing lens blanks L to engage tool51 at a speed faster than the desired predetermined slow speed. Theautomatic electrical means, Fig. 13, for controlling the above motorswill be discussed hereinafter. When the desired depth of cut is reachedon blanks L at said slow speed, motor 75 is then de-energized andconsequently again restricts sleeve 68 from rotation whereuponre-energization of motor 71 in a reverse direction to that previouslymentioned will cause lead screw 66 to rapidly withdraw from sleeve 68and move table 54 towards tool 52. The operation of the two feedmechanisms would be repeated in a similar manner for the fine generatingo'f blanks L and the return of table 54 to its starting position atwhich time both feed motors as well as spindle drive motor 58 would bede-energized to permit removal of block B from spindle 50.

A control mechanism, Figs. 9 and 10, for automatically controlling theoperation of motors 58, 71 and 75 is rigidly secured on the forwardupper surface of base 53 and comprises a circular housing 82 into whichone end of a shaft 83 projects. Shaft 83 is journaled in a rearwardlyextending bore 84 of a protuberance 84a formed in the base 53. Theopposed end of said shaft 83 is provided with a pinion 85 which, inturn, engages a rack 86 secured to the underside of table 54. Movementof table 54 will then cause rack 86 to rotate pinion 85 and consequentlyshaft 83.

In order to provide an intimate fit between the teeth 85a of the pinion85 and the teeth 86a of the rack 86 so as to eliminate the elfect ofbacklash and insure an accurate registry of the movement of table 54 bythe extent of rotation of shaft 83, the pinion 85 is provided with anadjustable annular segment portion 85b which is, in turn, provided withteeth 850 of substantially the same shape and pitch as teeth 85a.Segment 85b is clamped to pinion 85 by studs 85d which extend throughslotted openings 85e therein. Upon assembling rack 86 and pinion 85, theabove-mentioned backlash inherent in conventional rack and pinion drivesis eliminated by clamping segment 85b in a slightly rotated positionrelative to the body portion of pinion 85 so as to cause the leadingsurfaces of teeth 85a to engage one side of the adjacent teeth 86a ofrack 86 and the trailing surfaces of the matching teeth 85c tosimultaneously engage the opposed sides of teeth 86a of rack 86 wherebyeach of the combined teeth 85a and 85c will, upon meshing with rack 86,completely fill and intimately engage both sides of the adjacent spacingbetween teeth 86a of said rack.

The end of shaft 83 which projects into housing 82 is provided with apaddle-like switch actuating cam 87, rigidly secured thereon, which isadapted to alternately engage a plurality of electrical switches uponrotation of shaft 83.

Said cam 87 is so aligned on shaft 83 as to be in a vertical or neutralposition, as shown in Figs. 9 and 10, when the table 54 is in itsinitial starting position with block B substantially midway betweentools 51 and 52, as shown in Figs. 4, and 8. When in said neutralposition, the uppermost edge 88 thereof is in engaged relation with anelectrical switch 89 which is rigidly secured to housing 82. Switch 89functions to de-energize motors 58, 71 and 75 upon completion of agenerating operation as will be described in detail hereinafter.

Movement of table 54 in a direction toward tool 51 by energizing motor71 will then cause shaft 83 to rotate cam 87 in a clockwise direction,as viewed in Fig. 10, whereupon the lower portion 90 thereof, Fig. 11,will subsequently engage the plunger 91 of an electrical switch 92 whichis adjustably mounted on housing 82. Switch 92 then functions totie-energize motor 71 and energize motor 75 at a point just prior to theengagement of lens blanks L with tool 51, so as to cause motor 75 tooperate at its first-mentioned slow speed until blanks L reach a pointimmediately prior to engaging tool 51.

Cam 87 meanwhile has continued to rotate and at the instant beforeblanks L engage tool 51, the area 92 of cam 87, Fig. 10, will engageplunger 93 of a second electrical switch 94 which switch, in turn,functions through the electrical control means of Fig. 13 to cause motor75 to operate at its ultimate still slower speed throughout the cycle ofthe rough abrading of the RP curve on blanks L. Upon reaching thedesired depth of cut, which is limited by adjustably positioning a thirdelectrical switch 95 having a plunger 96 upon housing 82, the upper sidesurface 97 of cam 87 will then engage plunger 96 and 11 cause switch 95to function to de-energize motor 75 and energize motor 71 in a reversedirection to its initial starting direction of rotation and therebycause table 54 to retract from tool 51 and proceed at a fast speedtowards tool 52, as described hereinabove.

Said movement of table 54 towards tool 52 will then cause cam 87 torotate in a counterclockwise direction, as viewed in Fig. 9, until itcontacts the plungers 98, 99 and 100 of switches 101, 102 and 103,respectively, which function to control motors 71 and 75 through thecircuits of Fig. 13 in a manner identical to that of switches 92, 94 and95. Upon finally contacting plunger 100 of switch 103, cam 87 and table54 are returned to their initial starting position by again electricallyreyer-sing the direction of rotation of the fast-speed motor 71. Uponreaching its neutral position, the upper edge surface of cam 87 engagesswitch 89 which, in turn, deenergizes both motors 71 and 75 and motor 58to permit removal of block B from spindle 50.

As previously mentioned, switches 92, 94, 95, 101, .102 and 103 areadjustably mounted within housing 82 to permit the location of the upperends of the respective plunger portions 91, 93, 96, 98, 99 and 100 to beso positioned relative to each other and to the cam 87 as to properlycontrol the extent of movement, speeds and directions of travel of table54. By referring to one of the two groups of three switches, namely,101, 102 and 103, it can be seen from Figs. 9 and that this posi-.tioning is accomplished by mounting switches 101 and 102 upon a bracket104 and switch 95 upon a similar shaped bracket 105. Bracket 105 isrigidly attached by means of studs 106 to an outer adjusting ring 107rotatably mounted on an annular forwardly extending shoul dered portion108 of housing 82. Said studs 106 extend through ring 107 and arethreadedly engaged in an integrally formed slide portion 109, Fig. .10,of the bracket 105 which is slidably fitted in a guide slot 110 of theshouldered portion 108. Rotation of ring 107 will then cause bracket 105and switch 103 to rotate in unison and in order to retain said bracketin a desired adjusted position relative to cam 87, a clamp screw 111 isprovided which extends through ring 107, slide portion 109 andthreadedly engages a gib 112, Fig. 11, which upon tightening of clampscrew 111 will engage the inner surfaces of shoulder 108.

Since it is necessary to adjust bracket 104 and attached switches 101and 102 relative to switch 103 for posi- .tioning the plunger 99 inproper relation with plunger .100'to determine the depth of cut inblanks, which depth is controlled by the extent of travel of cam 87between plungers 99 and 100, bracket 104 is constructed similar tobracket 105 in that a slide portion 113, Fig. 10, is fitted into slot110. However, bracket 104 is retained in its desired adjusted positionon ring 107 solely by means of a clamp screw 114. Loosening of clampscrew 114 will permit bracket 104 to be slidably adjusted along ring107.

Switches 101 and 102 may also be adjusted relative to each other uponbracket 104 by loosening screws 115 which may be moved in slots 116 ofsaid bracket. 7

By properly adjusting switches 101, 102 and 103 and tightening screws115 and 114, said switches may then be moved as a unit by loosening lockscrew 111 and rotating ring 107 to a desired position relative to theneutral position of cam 87 and said movement is recorded by suitableindicia 117 provided on the outer surface of ring 107 to be matched withan indicating mark 118 on the stationary portion of housing .82. Saidindicia is graduated to record the settings used to provide the desiredRP curves on lens blanks mounted on various sized blocks B.

The above described switches 101, 102 and 1103 ,in combination with theelectrical circuits of Fig. 13 control the operation of table 54 inconjunction with the fine or finish abrading operation and switches 92,94

and are used to control the rough. abrading operation in an identicalmanner and are also identical yconstructed' and assembled for rotationwith a second vrotatable ring 119 positioned in side-by-side relationwith ring 107 on shoulder 108 and having indicia 120 on the outersurface thereof to be aligned with an indicating mark 121. e e Theabrading tools 51 and 52 are each located upon the generating device bymeans of supporting brackets 122 and 123, which are bolted or otherwisesecured to the upper surface of base 53 thereof, Figs. 4, 8 and 11. Eachof said brackets are provided with spindle heads 124 and 125,respectively, which are pivotally mounted thereon at 51a and 52a inoverhanging relation with the movable table 54. Said heads are eachidentically con structed and each comprises a spindle housing 126 fittedin a longitudinal bore 127 extending through the for-' ward portionthereof, said spindle housing being clamped in said bore 127 by lockingstuds 128. A spindle 128 in each of heads 124 and 12.5 carrying anabrading tool at one end is journaled in housings 126 and is providedwith pulleys 130 at the opposed ends which, in turn are connected bybelts 131 to additional pulleys 132 on the drive spindles of motors 133and 133a mounted rear wardly of heads 124 and 125 respectively.

Radial racks 134 and 135 are provided upon each of the upstandingforward portions 136 and 137 of the respective brackets 122 and 123 eachhaving their centers of curvatures located at pivot points 51a and 52a.respectively.

A drive arrangement for tilting the head .124 about pivot point 51a isillustrated on head 124 of Fig. .8 and it is to be understood that head125 is identically constructed. Said drive arrangement embodies a pinion138 in engaged relation with rack 134 and mounted for rotation in head124. A worm follower 139 is mounted for axial rotation with pinion 13.8and is positioned .internally of a cavity 140, Figs. 4 and 8, formed inhead 124. Said worm follower 139 is, in turn, engaged by a worm gear 141which .is secured to and, rotatable with a transversely extending shaft142 journaled in said head 124 and having an outwardly extendingirregularly shaped end portion 143 to which a wrench or suitable handlemay be detachably applied when angularly adjusting head 124. Rotation ofshaft 142 will, through worm gear 141 and worm follower 139, causepinion 138 to move along rack 134 and tilt head 124 about pivot point51a. The angle of .tilt is recorded by suitable indicia 144 providedupon an indicating Plate 145 fixed for rotation upon the outwardly{extending portion 143 of shaft 142.

The electrical circuit, Fig. 13, for controlling :the above.- describedautomatic operation of the generating deYice functions as follows:

The symbols R1 through R13 schematically represent electrical relayswhich electromagnetically function to close or open contacts C1 throughC13 which are placed in the various lines of the circuit. Said contactsare each represented by a pair of short parallel lines illustrating abreak or normally open circuit in its respective line. However, thecontacts having a diagonal line shown .therethrough, each illustrate anormally closed circuit in their respective line and when activated by arelated .relay, function to open or break the circuit.v

The apparatus embodying the electrical equipment schematicallyillustrated in Fig. 13 is housed within an upstanding enclosure 146attached to the rear portion of the generating device, as shown in Fig.8, and a control panel 147 extends forwardly and centrally from saidenclosure so as to be easily accessible.

Control panel 147 includes a conventional variac 148 for selectivelycontrolling the speed of the work spindle motor 58 and a pair ofconventional variacs 149 and 150 for similarly controlling the speed of.slow-feed mo tor 75 wherein variac. 149. is used to control :the

of feed for rough generating and variac 150 controls the rate of feedfor the fine or finish generating. Said variacs are each provided withmovable rotor arms 148a, 149a, and 150a, Fig. 13, which are operated byindicating dials 1435, 14% and 1511b respectively, Fig. 8. Push buttonswitch 151 is used to start the generating cycle and push button 152 isused to stop the generating cycle whereas push button 153 is used tode-energize the complete control circuit including the work spindlemotor 58 and the slow-feed motor 75 for emergency purposes. Push button154 is used to jog motor 71 to the right and push button 155 is used tojog said motor to the left.

Said variacs and push buttons and motors are designated in Fig. 13 bylike reference numerals and the control switches 89, 92, 94, 95, 101,102 and 193 of Figs. 10 and 11 are also designated in Fig. 13 by likereference numerals.

It is pointed out that the contacts and switches of Fig. 13 areillustrated as being in the starting position. That is, all motors arede-energized and the work-carrying spindle 50 of table 54 is locatedcentrally between tools 51 and 52 prior to a generating operation, asdescribed above.

Current is initially fed to the electrical system by an alternatingcurrent three-phase circuit 155 from which leads 156, 157, and 158 areconnected to operate motors 133, 13311 and 71. Leads 159 are, in turn,connected to one pair of wires of said three-phase circuit to providereduced alternating voltage to the primary windings of a conventional 1to 1 ratio transformer 160 which then acts through its secondarywindings to provide a lowvoltage supply for operation of the remainingportion of the illustrated circuit.

The generating cycle is started by depressing push button 151 which actsto energize relays R1, R2, R3, and R4 in succession and simultaneouslyoperate contacts C1, C2, C3, and C4. This is accomplished by supplying aflow of current from one side of transformer 160 through lead a,normally closed push button 153, lead b, lead which includes normallyclosed push buttons 154, 155 and 152, lead d, push button 151, R1, leade and to the opposed side of transformer 169. R1 then acts to operateall contacts C1 whereupon current will then flow from transformer 160,through lead a, push button 153, lead b, lead c, push buttons 154, 155,152, C1, R2, lead 2 and to transformer 160. R2 being thus energized, allcontacts C2 will operate whereupon R2 will be held energized throughbypass leads and C2. R3 is energized through a circuit from transformer160, lead a, lead 11, lead c and push buttons 154 and 155, lead g, leadh, closed switch 95, C1 which was closed by R1, normally closed C4, R3and lead e to transformer 160. R3 will be held energized by bypass lead1' and closed contact C3. R4 is energized through a circuit fromtransformer 160, lead a, lead b, lead c and push buttons 154 and 155,lead g, lead 1' including now closed contacts C3 and C1 and normallyclosed contacts C8 and C13, R4, lead e to transformer 160. R4 will beheld energized by bypass lead k including now closed contact C4.

Upon releasing push button 151, R1 will again be deenergized and allcontacts C1 will return to their initial open condition.

With R2, R3 and R4 energized and their associated contacts C2, C3 and C4operating as described above, relays R5, and R6 will be simultaneouslyenergized through the following circuits:

R5 is energized through a circuit from transformer 160, lead a, lead b,lead I which includes now closed contacts C2 and C3, R5 and lead e totransformer 161 R6 is energized through a circuit from transformer 160,lead a, lead 5, lead 1 including now closed contacts C2 and C3, lead inincluding now closed contact C3, lead 12 including switch 92 having oneside normally closed and R6 and lead e to transformer 160.

With relays R5 and R6 now energized, their associated contacts C5 and C6will now operate to energize the rough grind tool motor 133 and thefast-feed motor 71 to rotate in a direction suitable to drive table 54and spindle 50 rapidly toward the rough grind tool 51 and also energizethe work-spindle motor 58.

Motor 133 is energized by the closing of its contacts C5 to complete acircuit from lines through leads 156.

Motor 71 is energized by the closing of its contacts C6 to complete acircuit from lines 155 through lines 158.

Motor 58 is energized through a circuit from transformer 160, lead a,lead b, lead 0, now'closed contact C5,

and lead pwhich enters a conventional direct current rectifier andcontrol unit 161 embodying the speed control variac 143, which unitconverts the alternating current supplied thereto into direct current tooperate the conventional direct current motor 58. The circuit thenreturns from unit 161 to transformer through lead q, lead r and lead e.

With the table 54 of the generating device thus rapidly moving towardstool 51, the switch actuating cam 87, Figs. 10 and 11, ultimatelyapproaches and activates switch 92 at a predetermined point spaced agiven distance from the tool 51, as previously described.

Switch 92, being of a double contact type as schematically illustratedin Fig. 13 causes the circuit in line It to be opened by one set of itscontacts and, consequently, relay R6 to be dc-energized and itsassociated contacts C6 to return to their initial open position whichopens the circuit through leads 158 to stop the fastfeed motor 71.However, the otherset of contacts in switch 92 simultaneously closes acircuit to energize relay R7. Said circuit from transformer 16d passesthrough lead a, lead 12, lead I which includes now closed contacts C2and C3, lead m which includes now closed C3, lead s which includes thenow closed portion of switch 92 and closed C3, R7 and lead e back totransformer 160.

By so energizing R7, its associated contacts C7 are closed to provide aclosed circuit to energize the slowspeed drive motor 75. Said circuitpasses from transformer 160 through lead a, lead b, lead .0, lead t to aconventional direct current rectifier and control unit 162 which issimilar in character to unit 161 and embodies a pair of variacs 149 and150 for controlling the speed of motor 75. The circuit returns totransformer 160 through leads u, r and e. Variac 149 controls the motorspeed for rough generating and variac 150 controls the motor speed forfine generating.

It will be noted that the closing of contacts C7 will connect the variac149 in circuit with the unit 162 and motor 75. However at this time,with switch 94 in the position illustrated, the rotor arm 149a of variac149 is bypassed and thus causes motor 75 to operate at its initial slowspeed until table 54 and blanks L reach a point spaced a given distancefrom the tool 51 whereupon cam 87, Figs. 9 and 10, will function asdescribed previously to actuate switch 94 which, in turn, will cause thevariac rotor arm 149a to be connected in the variac circuits to unit 162and enable the still further reduction of the speed of motor 75 in aconventional manner in accordance with the selected positioning of saidarm by manipulation of the dial 14% at the control panel 147, Fig. 8.Variac 150 is, of course, disconnected from the circuit to motor 75since contacts C11 are open.

With the lens blanks L now advancing into tool 51 at said furtherreduced slow speed, the above-mentioned cam 87 will next activate switch95 at the point where the d sired depth of cut on lens blanks L isachieved.

Upon activating switch 95, the circuit in line It is opened and,consequently, R3 is de-energized. This, in turn, returns all contacts C3to their initial open or closed position. By so doing, relay R7 isde-energized which opens contacts C7 on slow-speed motor 75 to stop sameand disconnect variac 149 from the control unit 162 and motor 75. Simltan o s y, r lays. R9 and R10 ar e gized through the followingcircuits:

R9 is energized through, a circuit from transformer 160, through lead a,lead b, lead I which includes now closed C2, lead v which, includesnormally closed C3 and now closed C4, R9, and lead e to transformer 160.

R10 is energized through a circuit from transformer 160 through lead a,lead' 11, lead I which includes now closed C2, lead v which includesnormally closed C3 and now closed C4, lead x which includes now closedC4 and the normally closed portion of switch 101, R10, and lead 6 totransformer 160.

-By thus energizing R9 and R10, contacts C9 and C10 are closed and theworlespindle motor 58 continuesto operate through C9 which isloeatedbetween leads and p. The rapid feed motor 71 again is energized but in areverse direction to its initial directionof rotation by the closing ofcontacts C in the reversed connecting lines 158a. The fine grinding toolspindle motor 133a is also energized by the closing of contacts C9 inits lines 157.

With the motors thus operating, the table 54 of the grinding device israpidly moved towards the fine abrading tool 52 and upon reaching apredetermined point spaced a given distance from the tool 52, switch 101is activated bycam 87 of Figs. 10 and 11. Switch 101 being of a doublecontact type similar to that of switch 92, then acts to open the circuitin lead x to de-energize R10 and close the circuit in lead y to energizeR11.

Hyde-energizing R10, theirapid-feed motor 71 is deenergized and stoppedby the opening of C10 in lines 158a and by energizing R11, the slow-feedmotor 75 is energizedito rotate in a reverse direction to its initialdirection of rotation by the closing of contacts C11 in its leads fromcontrol unit 162. The closing of contacts C11 also connects variac 150in circuit with the control unit 162 and motor 75. Switch 102, however,being in its opened position as illustrated, disconnects the rotor arm150a of variac 150 to cause motor 75 to operate at its initial slowspeed, thus continuing to move lens blanks L toward tool 52. At a pointimmediately prior to the engagement of lens blanks L with tool 52,however, cam 87, Figs. 10 and 11, actuates switch 102 to connect therotor arm 150a into an electrical circuit through the variac 150 to thencause motor 75 through control unit 1.62 to operate at a still slowerpredetermined speed in accordance with the setting of said arm 150a. Thefinish generating of lens blanks L then proceeds until the de sireddepth of cut is reached at which time cam 87, of Figs. 10 and 11,actuates switch 103 which is also a double contact type similar to 101and 92. Switch 103 then opens the circuit in lead y to de-energize R11and closes the circuit in lead 2: to energize R12.

By so tie-energizing R11, contacts 11 are opened and motor 75 is stoppedand the variac 150 is again disconnected from the circuit through unit162 to motor 75.

When R12 is energized, contacts C12 are operated and provide a closedcircuit through a conventional timiug device 163 such as a cycleflextimer or the like. This timing device provides a controlled delay in themovement of table 54 to permit the fine generating tool 52 to completelyclear the RP surfaces of lens blanks L while table 54 remainsmomentarily stationary at the end of the feed cycle. This provides asuperior fine generated finish on said RP surfaces.

By the closing of contacts 12, a circuit is provided through R8 toenergize same. Said circuit is as follows: from transformer 160, lead a,lead I), lead I including now closed C2, lead v including now closed C3and now closed C4, lead at including now closed C4, lead x lead yincluding the now closed portion of switch 101 and C4, lead z throughthe now closed portion of switch 103, lead a including now closedcontact C12, lead g through R8, and lead 0 back to transformer 160. R8will then be held in :its energized condition by the closice of contactC8 in line 8- At he nd f he min yc e f me contact T in lead r which isoperated by timer 163, closes. This energizes R13 and closes C13 in leadm. energized'through a circuit from transformer 160, lead a, lead b,lead r including now closed contact T and R13, lead e to transformer160.

By closing contact C13 in lead m, relay R6 is again energized through anew circuit. Said circuit from-transformer 160 passes through lead a,lead b, lead c including closed push buttons 154 and 155, lead gincluding closed switch 39 and now closed contact C8, lead m includingnow closed C13, lead It including the now closed portion of switch 92,R6 and lead e to transformer 160.

By thus energizing R6, contacts C6 will close in lines 158 to operatethe rapid-feed motor 71 in its original starting direction of rotationto cause table 54 of the generating device to travel back toward itsinitial starting position midway between tools 51 and 52. Upon reachingsaid starting position, cam 87, Figs. 9 and 10, will'then actuate switch89 and open the circuit in lead g thus de-energizing R8 and consequentlycausing con-. tact C3 to open and simultaneously open the circuit to R6which will open contacts C6 on motor 71 to stop the table 54 at saidstarting position. The work-spindle motor 58 and the tool motor 133a hadpreviously been stopped when relay 13 was energized since R13 had openedthe normally closed contact C13 in lead j which de-en ergized R4 which,in turn, opened contact C4 in lead v to also de-energize R9. R9 thenacted to open contacts C9 in the leads to both the motors 133a and 58.

The above-described automatic generating operation would then be againrepeated by depressing the cycle start push button 151. a

In order to jog the table 54 along its path of travel in eitherdirection independently of the above automatic cycling operation forpurposes of aligning the various parts of the machine during a settingup operation or the like, a pair of jog push buttons 154 and areprovided in the circuit. Said push buttons function to move table 54 byoperation of motor 71 only when they are depressed and the movementinstantly stops when they are released. It is pointed out that only themotor 71 can be operated by the jog push buttons 154 and 155.

The operation of push buttons 154 and 155 is as follows: 1

Push button 154 is used to jog the table 54 to the right or in thedirection of tool 51. By depressing either button 154 or button 155, theelectrical circuit to relays R1, R2, R3 and R4 which passes through lead0 is opened thus preventing the automatic cycling operation, describedabove, from functioning. When the push button 154 is depressed, itssecond contact portion 154a which is interconnected therewith closes adirect circuit to relay R6 only when the switch 92 is in the positionshown in Fig. 13, when the cam 87 (Figs. 9 and 10) is not in contactwith switch 92. a

If it is desired to jog the fast-feed motor 71 to move.

table 54 to the right, switch 92 would be in the position illustrated inFig. 14 whereupon the closed circuit to R6 would be from transformerthrough lead a, lead b, lead n now including closed switches 154a. and92 through R6 and lead a to transformer 160.

As described previously, R6 closes contacts C6 in lines to motor 71 andcontacts 06 operate to cause motor 71 to move table 54 towards tool 51.When the table 54 reaches a position where the switch 91 is engaged bythe cam 87 (Figs. 10 and ll) the circuit to R6 is opened and contacts C6are likewise opened to automatically stop the right-hand direction oftravel of the table 54. At this time, however, the cam 87 is not inengagement with switch 101 and the table 54 can be jogged to the left ortowards the tools 52 by operation of the jog push button 155 as follows:

The jog push button 155 operates in a manner identical to button 154 andits second contact 155a, when closed,

R13, is now 17 energizes R when the switch in Fig. 13. With switch 101in the position illustrated and button 155 depressed, R10 would beenergized through a circuit from transformer 160, lead a, lead b, lead yincluding now closed button 155a, lead x lead x including closed portionof switch 101, R10 and lead e to transformer 160. With R10 energized,the contacts C10 will close to energize motor 71 in such manner as todrive the table 54 to the left and to the point where the cam 87contacts switch 101 and opens the circuit in lead 2: to tile-energizeR10 and open contacts C10 to stop motor 71. It is pointed out that thejog push buttons 154 and 155 only function to operate motor 71 and withthe cam 87 (Figs. 9 and 10) out of engagement with switches 92 or 101,said switches will automatically assume the positions shown in Fig. 13.Therefore, the table 54 can be jogged either to the right or leftbetween the limits of switches 92 and 101 by operation of the respectivejog buttons 154 or 155.

Push button 153 is positioned directly in the control circuit line foremergency purposes. That is, by depressing button 153, the completecontrol circuit is de-energized and all of the motors are instantlystopped. Upon releasing push button 153, the. motors will remaindeenergized since all the relays have been de-energized. However, thecycle may again be started by depressing the cycle start button 151.

Having generated the RP curve and lens blanks L in the manner describedabove, block B is then-removed from the generating device. The generatedRP surfaces thereof are then provided with an optically polished finishby means of a suitable polishing apparatus. A diagrammatic illustrationof such an apparatus is shown in Fig. 12 wherein the block B ispositioned upon one end of a rotatable shaft 165 journalled in a base166 of said apparatus. Shaft 165 is powered by a pulley 166 and belt 172which is, in turn, connected to any suitable source of power such as anelectric motor or the like 167. A circular polishing pad 168, having alens engaging surface preformed to substantially match the curvature ofthe lens surface to be polished and preferably formed of a suitableplastic composition or any of the conventional polishing materials knownto the trade is positioned in engaged overlying relation with the abovegenerated reading portion surfaces, as illustrated in Fig. 12. Saidpolishing pad 168 is mounted at one end of a supporting spindle 169which is journaled in an angularly disposed supporting head 170 and isrotated about its axis by a pulley 171 and belt 172, which belt 172functions to rotate both spindle 169 and shaft 165, as illustrated.

The curvature of the RP surfaces of the lens blanks L, having beenformed as described above are monaxial with the curvatures of thereference surfaces 10 wherein both the centers of curvature of said RPand reference surfaces of each of said lens blanks lie on a common axisthrough the dividing line 12thereof. Thus, the center of curvature ofthe generated RP curve on each of the lens blanks L is located on theaxis of rotation 173 of block B at the point of intersection 174 of aplane through the dividing lines 12 of the blocked lens blanks L. Itwill be noted that the axis of spindle 169 is tilted about said centerof curvature 174 to cause the lens engaging surface of the polishing pad168 to properly seat upon the RP surfaces of lens blanks L. Thepolishing procedure is accomplished by simultaneous rotation of block Band polishing pad 168.

By the proper selection of a conventional polishing medium to be appliedto the lens blanks L and polishing pad 168, the lens blanks andpolisihng pad may be rotated at relatively high speeds to reduce thetime of polishing.

The lens blanks L are then removed from block B.

It is pointed out that each of the above lens blanks L are subsequentlyfinally finished as one piece multifocal lenses by grinding andpolishing the concave sides thereof to predetermined curvatures such asto give the fields 101 is closed as shown 10 and 11 predeterminedoptical powers controlled in accordance with the prescriptiverequirements of particular individual wearers. The grinding andpolishing of the concave sides of the lens blanks L may be accomplishedby any one of the well-known conventional lens surfacing techniques usedto form continuous optical surfaces on lens blanks.

A modification of the above-described lens blank surface generatingmachine of Figs. 4, 8, 9 and 10 is illustrated in Figs. 14-18. Thismodification consists broadly of an auxiliary drive mechanism 200 whichis provided on the head of the generating machine to cause the fineabrading tool 52-and its associated spindle-supporting mechanism to bemoved axially toward the lens blanks L on block B during the finishgrinding of the RP surfaces thereof. By causing the tool 52 to fineabrade the lens blanks L with a plunge cut as by being moved in thedirection of its axis rather than fine abrading the lens blanks bymoving the same laterally into the tool, as described hereinabove, thefinish abrading cycle can be considerably speeded up without detrimentto the finally formed free edge of the dividing line 12 of the lensblanks since it will become apparent that the abrading edge of the tool52 which forms the finished cliff-like dividing line 12 on the lensblanks does not finally reach the ultimate finished location of saiddividing line 12 until the removal of substantially all of the materialfrom the reading section of the lenses has been completed. Furthermore,with the lens-generating machine of the invention modified as shown inFigs. 14-16, uneven wear on the effective abrading edge of the finishabrading tool is substantially eliminated and a superior finished RPsurface curvature is produced on the lens blanks which is of a truedesired radius of curvature throughout the entire surface area of saidRP surface including the area immcdiately adjacent the dividing line 12of said lens blanks.

To more fully understand the specific function of the drive mechanism200 and the advantages gained by so modifying the generating machine ofFigs. 4, 8, 9 and 10, particular reference is made to Figs. 14-16wherein it can best be seen in Fig. 16 that the spindle-supportinghousing 126 of the head 125 has been somewhat modified at its oppositeends. The modification of the spindle housing 126 consists of a threadedarea 201 adjacent its lower end which is threadedly engaged in aninternally threaded ring-like member 202 fixed to the underside of thehead 125 by studs or the like 203. The spindle housing 126 is journalledin the bore 127 extending through the head 125 so that rotation of thehousing 126 in one direction will cause its threaded area 201 to advanceinto the member 202 and lower the abrading tool 52 towards the block Bwhereas rotation of the spindle housing 126 in the opposite directionwill raise the tool 52 away from block B. The tool 52 is fixed to thelowerend of the spindle 126 by studs or the like 204 and the spindle 129is independently rotatable within its housing 126, as describedhereinabove with reference to Fig. 8.

Means to rotate the spindle housing 126 within the head 125 is providedat its upper end and comprises a splitring gear 205, see Figs. 14, 15and 16, in surrounding clamped relation with an adaptor 206 which issecured to the upper end of the spindle housing 126 by studs or the like207. The adaptor 206 is provided with a central opening 208 throughwhich the spindle 129 extends with suflicient clearance to permit thesame to be independently rotated within its housing 126. The uppermostend of the spindle 129 is provided with the usual pulley 130 and belt131 drive mechanisms shown in Figs. 4 and 8 by means of which thespindle 12? and its attached abrading tool 52 are continually rotatedabout their axes during the time abrading of the lens blanks L.

Rotation of the spindle housing 126 to lower or raise the tool 52, asthe case may be, relative to the blocked lens blanks L is brought aboutby operation of a conventional reversible electric drive motor 209 whichis geared aaaa as 19 through a conventional reduction drive 210 to thering gear 205 (see Figs. 14 and The drive train from the reduction drive210 to thering gear 205 embodies a shaft 211 havinga worm gear 2.12.adjacent its lowermost end in meshed relation with a worm follower 213which is pinned or otherwise fixed to one end of a transverselyextending shaft 214. The shaft 214 is'journalled in the upper portion ofthe head 125 of the generating machine and carries a worm gear 215whichmeshes with and drives the ringgear 205. Rotation of the motor 209 inone direction will revolve the ring gear 2&5, adapter 2% and the spindlehousing 126 about its longitudinal'axis to cause its threaded part 201to advance into the member 202 and lower the tool 52 towards the blockedlens'blanks L whenlocated thereunder. Rotation of the motor 299 in anopposite direction will cause the spindle housing 126 to be oppositelyrotatedgand retracted from the threaded member 202. i

In the generating of the RP surfaces on the lens blanks L with thelens-generating machine of the invention which has been modified asshown in Figs. 14, 15 and 16-, the rough'generating cycle is performedprecisely as described hereinabove by first moving the blocked lensblanks L transversely into abrading relationship with the rough abradingtool 51 until a desired depth of cut is obtained whereupon the blockedlens blanks are withdrawn from the tool 51 and moved in the direction oftool 52 to be finish abraded by removing a desired amount of materialfrom the rough abraded RP surfaces whilev simultaneously removing theexcess of material adjacent the ultimate finished locationof thedividing line 12 on the lens blanks LI As described in detailhereinabove., this excess of material is left on the lens blanks duringthe rough abrading thereof to protect the immediate area inwhich thedividing line 12 is to be finally formed by tool "52 from damage dueto'po'ssible glass flaking which might be caused by the coarseness ofthe abrading particles of the rough abrading tool 51. Having been roughabraded, the blocked lens blanks Lv are moved transversely towardstool'52 to the exact location or point at which the feed or motion ofthe lens blanks is stopped at the completion of the finish abradingcycle in the operation of the machine of Figs. 4, 8, 9 and 10 which wasdescribed in detail hereinabove. It is pointed out that this point atwhich the transverse movement of the lens blanks toward tool 52 isstopped, is such as to cause the axis of the spindle 129 and tool 52 tointersect the axis of the spindleSO and block B at the point ofintersectionof the plane of the axes 13 of the lens blanks L on saidblock B (see Fig. 16,). In this manner, the distance and reading fieldsof each of the finally finished lens blanks will be monaxial with theircenters of' curvatures lying on the axes 13, as shown more particu'larly in Fig. 2. During the movement of the block B towards the tool 52as justdescribed, the tool 52 is in a retracted or. raised position soas to have its effective abrading edge in close proximity to the roughabraded tionary during the finish abrading of the RP surfaces of thelens blanks L. Spindle 50 is rotated by rno'tor 58 to,

revolve the block B and lens blanks L thereon aboutthe axis of saidspindle 50 and the tool 52 is simultaneously revolved about its axis bymotor 133a. The motor 269. is energized and the tool 52 is moved intoabrading relation with the lens blanksL by the threading of the spindlehousing 126 into the member 202. Thus, the movement 4 of the tool 52 isin a direction along its axis towards. the lens blanks L. This movementis continued until. the eifective abrading edge of the tool 52, reachesthe'final.

depth of cutas illustrated in Fig.7 1 8 1whereinfthe divi ing;

line 12 on the lens blanks has beenfinish .abraded..to a depth,Sufiicient'to lo'cate said dividing line .12 on theaxis 13 of theblanks. In referring moreparticnlarly to Figs. 17 and 18, itcan be seenthat the excess of material on ing the finish abrading cycle canbeconsiderably increased" over that described above with reference to thegenerat ing machine of Figs-'4, 8, 9 and 10 .whichis not modified asshown in Figs/l4, and -l,6"sinc e anypossible slight glass flaking whichmight result during the finish abradingof the lens blanks with thearrangement shown in Figs. 7 7

l4, l5 and 1 6'will not take place at the ultimate desired location ofthe dividing line 12 on axis 13-,due to the fact that the effectiveabrading edge of the-tool which forms the dividing line 12 does notengage said location until the instant the final depth of cut isreached. Upo'n reaching the final depth of cut, the feed motor 20? isstopped and rotation of the tool 52 and block B is coninued for a shortdwell period to clear the fine abraded RP surfaces and produce a cleanout free edge and shoulderat the dividing line 12.. This operation isreferred to n t trade as p r n ut o the lensb ank surfaces. a drp s aSuper o fin sh 0 the RP surfa e t is u h m ted ou at ddit ghtq he s i upof n e r n c e u ev nness n h we r on e o 5 is e de it he u e of h a ranem nt shown in Figs.14- -1 since all parts of the effective abrad: nsurface re of he t l 5. h h f rm th RP ra iu of curvature are inconstant engagement with the lens blank at all times. While thearrangementof Figs. 4, 3. and ,0 has produced. ve e ta tery shhs in t efinish abrading of lens blanks, there is some tendency for the tool 52to wear slightly. unevenly during the abragl; ing o the ahhve e x e s ofm t a leh adiwh the axis 1 3 ofthe lens blanks. In moving thelens blanksinto the tool 52, as described with reference; to figs. 4, 8 9 and 10,the major portion of said excess-of materim must be abraded away beforethe completeinner radially shaped abrading face of the tool engagetherough abraded RPl surfaces oithe blanks. the ter. poi tionjofthe to'ol.SZ whichfirSt abiades the ss, f, material adjacent the axes 1 3 of theblanket .tobecom e slightly misshapen hy wear with the resultthat aslight radiusfor error in the portion of the finished RB curveimmediately adjacent the dividing line 12rni'ghtr'esult.

With the arrangement showniniFig'si 14. 16, such a condition issubstantially completely avoided: andasharp and clean-cut joinderbetween thef dividingv line; 12 and the finished RP surface is assured iWhen the final depth of cutfis. reached by thelool 52 in the. device ofFigs. 14-16, the motor. 299 tie-energized by the actuation of amicio-switchj216 Twhitih is engaged by aprotrudingstoprnembe 217; Theicro.-swi tch';,2 1,6 is fixed tofthehea'd of th v stop'member 217 isf.o r.rn e das anintegral 'dttt ardlyprojectingf portion of thering gear205; ringfgearltli n r i ed h bhra emihhedz l s p 5 idedto prhdue.asnper qnfinishwn;t e 'R urfa s f eneraiirigma'chine d, the.

the table 54 of the generating machine is withdrawn from the tool 52 bybeing moved transversely back to its initial starting position centrallybetween the tools 51 and 52, as shown in Fig. 8. At the same time, themotor 209 is energized to rotate the spindle housing in such a directionas to retract the housing and return the tool 52 to a po'sition such asshown in Fig. 16 wherein it will again be ready to receive other lensblanks to be finish abraded as described above.

In order to accuraely locate the tool 52 in a raised position so as toproperly receive the lens blanks, as shown in Fig. 16 and as describedabove, prior to each finish abrading operation, a second stop member 220is provided in clamped relation between the ring gear 205. and theadaptor 206 so as to rotate with the ring gear, adaptor and spindlehousing assembly. The second stop member 220 is adapted to engage andthereby activate a second micro-switch 221 which is fixed to thehead125. and de-energize the motor 209 when the tool 52 is retracted orraised to the above-described proper position. The stop member 220 is anoutwardly projecting part of a shim-like collar member 222 which isfitted between the ring gear 205 and the adaptor 206 and said stopmember is initially radially adjusted relative to the stop member 217and switch 201 about the axis of the spindle housing 206 by looseningthe clamp screw.219 of the ring gear 205. With the stop members 217 and220 properly adjusted relative to each other and to their re: spectivemicro-switches 216 and 221, the clamp screw, 219 is tightened tosecurely clamp the respective parts of the above assembly together.

It is pointed out that upon completion of the finish. abrading cyclejust described, the lens blanks are deblocked and further processed asby polishing with the device of Fig. 12 in precisely the same manner asdescribed hereinabove.

In adapting the auxiliary drive mechanism 200 of Figs. l4, l and 16 tothe generating machine of Figs. 4, 8, 9 and 10, a modification of theelectrical system shown in Fig. 13 is required and this modification isillustrated in Fig. 19, wherein the contacts C14, C15, C16, C17,switches 216 and 221, relays R14, R15, R16, R17 and motor 209 have beenadded to the electrical system shown in Fig. 13.

As stated hereinabove, the rough generating of the RP surfaces on thelens blanks L with the lens generating machine of the invention whichhas been modified as shown in Figs. 14, 15 and 16 is performed preciselyas described with regard to Fig. 13.

After the completion of the rough generating cycle, the table 54 of thegenerating machine automatically moves to the left or towards tool 52 byoperation of the motor 71. Upon approaching the vicinity of the tool 52,the cam 87 (Figs. 9 and engages the micro-switch 101 which acts tode-energize relay R10 by opening the circuit through line x. At the sametime, switch 101 being of the double contact type as shown in Fig. 19,closes the circuit in line y to energize relay R11 Upon energizing R11,its associated contacts C11 are immediately closed and motor 75 isenergized to continue the movement of table 54 towards the tool 52 tothe point where the cam 87 engages micro-switch 103 (Figs. 9, l0 and19), which, in turn, opens the circuit in line y tode-energize relay R11and thereby open its associated contacts C11 to deenergize motor 75 andstop the table 54. The table 54 is, at this time, located in a positionsuch as illustrated in Fig. 16. As described in detail hereinabove, thisposition at which the table 54 is stopped is such as to cause the axisof tool 52 to intersect the axis of block B at a point thereon whichlies in the plane of the axes 13 of the lens blanks L onthc block B. Theswitch 103 being of the double contact type as described with referenceto Fig. 13 and as shown in Fig' 19, closes the circuit in line 2 whenengaged by cam 87. The closing of the circuit in line z then energizesR17 through the normally closed 22 portion of switch 216 which is of thedouble contact type as illustrated. R'17 being energized causes itsassociated contact C17 in the circuit to motor 209 to become closed. Atthe same time, the contacts C17 in the circuit to the variac are closedthereby connecting the rotor arm 150a in circuit with the unit 162 andmotor 209. In so doing, motor 209 will rotate the spindle housing 126and thereby lower the tool 52 towards the lens blanks L in a directionalong the axis of tool 52. It is pointed out that the speed at which,the motor 209 operates is con trolled by the preselected positioning ofthe rotor arm 150a of the variac 150. The operation of motor 209 tcontinues until a desired depth of finish cut on the lens blanks L isachieved, at which time the stop member 217 on the drive gear 205 (seeFigs. 14 and 16), engages micro-switch 216 to open the circuit throughR17 and de-energizes the same (see Fig. 19) where-by the abovementionedcontacts C17 will, accordingly, be opened and the motor 209 will bede-energized thereby stopping the downward travel of the spindle housing126 and tool 52. Switch 216, being of the double contact type, as shownin Fig. 19, when actuated by the stop member 217 automatically closesthe circuit through line z to energize R12. When energized, R12 closesthe normally opened contact C12 to complete a circuit through the timer163 to start the same and provide the above-described dwell periodwherein continued rotation of the block B and the tool 52 about theirrespective axes will clear the fine abraded RP surfaces of the lensblanks to produce a superior finish thereon. At the end of the dwellperiod, the timer 163 will automatically close contact T in line r whichwill cause relays R13 and relay R16 to become energized.

Upon being energized, R13 closes contact C13 in line m to energize R8and R8, in turn, closes contact C8 in line g to hold R8 in its energizedcondition by the circuit in line g through switch 89 and C8. Theenergizing of R8 also causes contact C8 in line (which is normallyclosed) to open and thereby de-energize R4 which causes its normallyclosed associated contact C4 in line h to close and energize R3 by thecircuit through line It. With R3 energized and its associated contact C3in line s closed, R7 will be energized causing contact C7 in the leadsto motor 75 to close. This starts motor 75 and causes the table 54 tomove to the right or in the direction of tool 51. Upon reaching theapproximate center of the machine or location at which the lens block Bwas positioned at the beginning of the lens abrading cycle before beingrough abraded by tool 51, the cam 87 (see Figs. 9, 10, 19) will strikemicro-switch 89 causing the same to open the circuit in line g andthereby tie-energize R8. When R8 is de-energized, its associated contactC8 in line j will return to its normally closed position so as to againenergize R4. Immediately upon energizing R4, its associated normallyclosed contact C4 in line It, opens to de-energize R3. The de-energizingof R3 causes its associated contact C3 in line s to open and therebyde-energize R7 which stops motor 75 by opening contacts C7 in the leadsto said motor. meantime, R16 which was energized by the closing ofcontact T had caused contact C16 in line r" to close and energize R14and R15 through lines r and r". The energizing of R14 closes contact C14and thereby provides a hold circuit for R14 and R15 through line r,switch 221 and C14. At the same time, the energizing of R14 causescontact C14 in the lines to motor 209 to close and energize motor 209causing the same to operate in such a direction as to raise the spindlehousing 126 and tool 52 away from the block B and lenses L in adirection along the axis of tool 52. It will be noted that along withthe closing of the above-mentioned contact C14 in the lines to motor209, another contact C14 is simultaneously closed in the circuitsassociated with variac 150 to cause the rotor arm 150a of variac 150 tobe bypassed thus causing motor 209 to operate at its maximum speed.During the time interval in which motor 209 operates to In the

